The present invention relates generally to a fuel tank for a motor vehicle with a wall manufactured from plastic, in particular by the injection molding method.
Plastic fuel tanks are often used in present-day motor vehicles and are therefore known. In such cases, the fuel tank is usually composed of a plurality of parts manufactured by the injection molding method. Manufacturing the fuel tank by the injection molding method makes it possible to easily produce complicated shapes or insert build-in components. The fuel tank thereby becomes highly cost-effective.
The disadvantage of fuel tanks made of plastic is that fuel vapors may diffuse through the tank wall. This leads to unnecessary pollution of the environment by fuel vapors.
Thus, there is a need for a fuel tank of the type initially mentioned, that can be produced particularly cost-effectively and that as few fuel vapors as possible pass through its wall into the environment.
Other needs will become apparent upon a reading of the following description taken in conjunction with the drawings.
In one form of the invention, the aforementioned needs are fulfilled by a fuel tank, whereby the fuel tank wall contains at least two shells arranged one above the other, and the fuel tank has means for the removal of fuel vapors present in a gap between the shells.
By virtue of this design, the fuel tank has a double wall which prevents direct diffusion of the fuel vapors. The fuel vapors which have passed through the inner shell collect initially in the gap between the walls. Further diffusion through the second wall is prevented by the means for the removal of the fuel vapors. As a result, virtually no fuel vapors pass into the environment.
According to an advantageous development of the invention, the means for the removal of the fuel vapors are designed to be particularly cost-effective if they have a filter element arranged between the two shells for absorbing fuel vapors. Another advantage of this design is that noises emanating from the fuel tank are damped by the filter element.
According to another advantageous development of the invention, the means for the removal of the fuel vapors permanently prevent fuel vapors from escaping if they have, arranged on the outer shell, an inlet orifice and an outlet orifice for scavenging air. In this case, the scavenging air may be provided, according to choice, either alone or together with the filter element arranged between the shells, for the removal of the fuel vapors.
According to another advantageous development of the invention, any inadvertent escape of scavenging air laden with fuel vapors from the gap between the shells can be avoided if the inlet orifice and the outlet orifice are capable of being closed in each case by a valve.
According to another advantageous development of the invention, the fuel vapors can be eliminated by means of the scavenging air if a connection for a line leading to an internal combustion engine of the motor vehicle is arranged in the region of the outlet orifice. The scavenging air is thereby delivered to the internal combustion engine. The fuel vapors are subsequently combusted.
The filter element arranged between the shells could be exchanged, for example, after an intended timespan. However, this necessitates highly cost-intensive maintenance of the fuel tank. According to another advantageous development of the invention, regular exchange of the filter element can be avoided if the filter element is spaced from the shells. A gap, through which scavenging air can flow, is thereby located between the filter element and the shells. As a result, the filter element is cleaned by the scavenging air. By virtue of this design, there is no need for scavenging air to flow constantly through the gap between the shells. Throughflow can take place, for example, at intended time intervals.
The fuel tank according to the invention can be manufactured particularly cost-effectively if the means for the removal of the fuel vapors have a filter element arranged at the outlet orifice. Another advantage of this design is that the filter can be separated in a simple way from the remaining regions of the fuel tank. This results in the fuel tank according to the invention being recyclable in a particularly simple way. The fuel vapors are removed particularly reliably if the filter element contains activated charcoal.
A contribution to further reducing the manufacturing costs of the fuel tank according to the invention is made if spacers for separating the shells are manufactured in one piece with one of the shells. The spacers can be manufactured in one piece with one of the shells in a very simple way by the injection molding method. The shells can subsequently be assembled very simply.
According to another advantageous development of the invention, the shells can be manufactured in cost-effective, simply designed injection molds if the spacers are designed as a lattice-like insert part.
A contribution to a further reduction in the manufacturing costs of the fuel tank according to the invention is made if the filter element arranged between the shells forms a structural unit with the spacers.
The invention permits numerous embodiments. In order to make its principle even clearer, two of these are illustrated in the drawings and are described below.